No time to dig further but I also noticed two additions in the CS6 scriptui.xml prerelease file:

1) The EditText creation properties now include wantReturn, which only applies to multiple line edit controls in ScriptUI Version 6.0 or later. When true the RETURN/ENTER keystroke is considered as text-input advancing the cursor to the next line. The default value is false.

2) Also, the ListBox.columns property has a new inner parameter, visible, described as an array of boolean visible attributes, whose length matches the number of columns specified at creation. This property can be used to show/hide a column. Avaiblable in ScriptUI Version 6.0 or later provided ScriptUI.frameworkName == 'Flex'.

What puzzles me a lot is the condition: ScriptUI.frameworkName == 'Flex'

FWIW, I believe the original choice was made in the interests of a basic level of data privacy -- you couldn't get the value for a key without knowing the key. Not water-tight, but also not without its virtues.

Removed

Classes

FolioBindingDirectionOptions (enum)

FolioOrientationOptions (enum)

So, these and some of the others are because the DPS plugin was installed in your CS5.5 installation, and not because of changes to the CS6 DOM. I found it more useful to compare the 8.0$7.5 file with the 8.0$8.0 file. (I did a manual comparison of 8.0$7.5 with 7.5$7.5 first to be safe!).